Digital wireless communications have occupied an important position in communication fields due to developments of the techniques. However, wireless communications use public controlled radio-signal spaces, and thus, include a fundamental problem that a third party can receive data. Therefore, there is always a risk that the communication content is intercepted by a third party and the information leaks.
In order to overcome the problems, the processing is performed currently for encrypting the communication information to prevent information from leaking when the information is intercepted.
Encryption of information is studied in various fields, and is applied in a variety of fields. This is principally based on a significant feature that security is ensured to a certain extent without varying the communication system.
However, since it is not possible to prevent encrypted communication information from being intercepted by a third party, a problem arises that the third party decrypts the encrypted communication information from the intercepted received information by consuming time.